Extreme pressure lubricant



United States Patent EXTREME PRESSURE LUBRICANT 9 Claims. (Cl. 252-48) This invention relates to lubricants with extreme pressure properties, and more particularly, to grease compositions which possess a high film strength.

The lubrication of antifriction bearings Where very heavy shock loading is encountered, such as in steel mill rolling equipment, requires a lubricating grease which is capable of affording protection to the mechanical parts under conditions of extremely high unit pressure. Mineral lubricating oil, which is the essential lubricating element in the usual lubricating grease, is deficient in lubricating properties under extreme pressure conditions and can not per se meet the requirements for lubricating steel mill rolling equipment operating under enormous pressures.

Consequently, the conventional greases are not suitable.

In accordance with the present invention, a lubricating grease of unusually high film strength which meets all the requirements for steel mill rolling equipment and similar applications is provided.

It has been discovered that when a novel combination of ingredients, namely, sublimed blue lead and sulfurized sperm oil, is incorporated into lubricating grease compositions in a total concentration of at least 2 percent by weight and wherein the weight ratio of sublimed blue lead to sulfurized sperm oil is in the range of from about 1:3 to 1:5, unusually outstanding extreme pressure properties are imparted to the lubricating grease composition.

A surprising aspect of the invention is that when sublimed blue lead and sulfurized sperm oil are present in the aforementioned proportions with respect to each other, considerably improved results are realized over other combinations thereof or when these ingredients are employed individually. Although the total concentrations and ratios of these ingredients as given hereina'bove all provide superior results, it is preferred not to employ more than about percent by Weight of the grease composition of the combination of sublimed blue lead and sulfurized sperm oil in the ratios set forth above. This is so because with certain greases but not all, depending upon the viscosity of the lubricating oil base and the specific thickener employed to form the grease, amounts of the sublimed blue lead and sulfurized sperm oil in excess of about 10 percent by weight tend to break down the grease structure. Within the preferred total additive concentration of from 2 to 10 percent by weight, best results are achieved with weight ratios of sublimed blue lead to sulfurized sperm oil of 1:4 to 1:5.

sublimed blue lead is a basic sulphate of lead and has found application for many years as a rust-proof paint pigment. The raw material used in the manufacture of thisproduct is 'galena lead sulfide ore. This. ore shows about 80 percent lead. and 11 percent sulfur content in a Patented July 21, 1959 2 combination to form lead sulfide, the balance being zinc sulfide and other constituents. The ore is mixed in suitable proportions with bituminous coal and slag and then charged into furnaces. The furnaces are designed and operated to produce fumes that come off the molten charge. The fumes are filtered and the solid parts are retained. This retained, powder-like material is the sublimed blue lead which runs as follows upon analysis:

Percent PbSO, 45-55 PbO 30-40 PbS Not over 12 PbSO, v Notover 5 ZnO Not over 5 Carbon Not over 5 These components are in chemical combinations. A mechanical mixture of the proper amounts of exactly the same ingredients to give the same analysis does not produce sublimed blue lead.

The sulfurized sperm oil additive employed in the grease compositions of the present invention is itself well known in the art. Its preparation and properties are disclosed in US. Patent 2,179,066 to Smith. 'As shown therein, the sulfurized sperm oil advantageously has a sulfur content of from 8 to 14 percent by weight.

As is known in the art, the mineral lubricating oils used as bases in manufacturing greases include paraffinic, naphthenic and mixed base mineral lubricating oils. The thickening agents employed to thicken the lubricating oil base to a grease are themselves known in the art. The soap type thickeners include fatty acid soaps derived from fatty materials such as tallow, lard, cottonseed oil, hydrogenated castor oil, stearic acid, hydrogenated fish oil, fatty acids and various other fats and fatty acids. The metal of such soaps can be an alkali metal, for example, sodium or lithium, an alkaline earth metal, for example, calcium and various other metals such as lead, zinc, chromium, tin, aluminum, nickel, cadmium and the like. Non-soap thickeners, for example, finely divided silica, and the so-called bentones which are reaction products of bentonite and onium bases can also be employed. See U.S. Patent 2,531,440. As will :be understood by those skilled in the art, the thickener and mineral oil base will be selected in accordance with the specific properties of the grease it is desired to manufacture and its specific application. For extreme pressure greases which are particularly adapted for use in steel mill rolling equipment, it is preferred to employ as the soap base a lithium soap or hydrogenated castor oil and as the lubricating base a mineral lubricating oil having a Sayb0lt Universal viscosity of from 500 to 1200 seconds at F. In general, the lubricating oil base should preferably have a viscosity of about 1000 SUS at 100 F.

The greases of this invention can be prepared in the conventional manner. For example, fats and/or fatty acids are charged to an atmospheric or pressure/type vessel and intimately mixed at temperature below 200 F. After thorough intermixture, the temperature is raised to between 330410 F. to effect saponification. After complete dehydration of the soap base, the soap concentration is reduced by mixing with mineral oilwhile cooling to a temperature range of -250 F. A 'mixture of sublimed blue lead and sulfurized sperm oil in the proper proportions is then added to the greasecomposition. The product is finally adjusted to the desired consistency and milled.

The following examples are illustrative of the invention:

EXAMPLE I To a Stratford contaetor are charged 28.8 parts of Texas oil of a viscosity of 500 SUS at 100 F., 8.24 parts of hydrogenated castor oil, 0.93 part of prime tallow, 1.25 parts of lithium hydroxide monohydrate and 0.28 part ofwater. The mixture is heated to a temperature of from 400410 F. During this heating period internal pressure increases to approximately 100 p.s.i.g. and is then vented to atmospheric pressure before reaching maximum temperature. After dehydrating the soap base 11.3 parts of 500 SUS at 100 F. Texas oil is drawn into the contactor.

The grease is transferred from the contactor to a kettle equipped with means for agitation. Following the transfer, 4.18 parts of 500 SUS at 100 F. Texas oil is added together with.40.87.parts of 150 SUS at 210 F. Mid-Continent Bright Stock over a period of about 3-4 hours as the grease cools to 230-240 F. Following the reduction with oil a mixture containing 0.9 part of sublimed blue lead and 4.05 parts of sulfurized sperm oil is added to the grease with agitation.

Adjustment for a penetration corresponding to a No. 2 NLGI consistency is made by adding 4.92 more parts of S SUS at 100 F. Texas oil and 4.53 parts of 150 SUS at 210 F. Mid-Continent Bright Stock. In order to keep the percentages of sublimed blue lead and sulfurized sperm oil in the final product at 1.0 and 4.5 respwtively, 0.1 part of sublimed blue lead and 0.45 part of sulfurized sperm oil are added. The batch is finally thoroughly deaerated and milled.

The above grease had the following calculated composition in percent by weight.

Make-up: Percent by wt.--

500 SUS at 100 F. Texas oil 43.50 150 SUS at 210 F. Mid-Continent Bright Stock 41.10 Lithium soap of hydrogenated castor oil 8.10 Lithium soap of tallow 0.90 Glycerine 0.90 Sublimed blue lead 1.00 Sulfurized sperm oil 4.50

EXAMPLE II A similar grease was prepared according to the procedure of Example I. The grease had the following composition in percent by weight. Make-up: Percent by wt.--

500 SUS at 100 F. Texas Oil 40.09 1900 SUS at 100 F. Texas oil 44.07 Lithium soap of hydrogenated castor oil 8.18 Lithium soap of tallow 0.91 Glycerine 0.36 Excess lithium hydroxide 0.09 Sublimed blue lead 1.30 Sulfurized sperm oil 5.00

EXAMPLE HI Another grease prepared according to Example I had A standard test which is used to determine the extreme pressure characteristics of an industrial lubricant is the well known Timken test. Essentially the Timken test is conducted in a machine which rotates a steel test ring at 800 R. P. M. against a stationary steel block. Pressures between the ring and the test block are regulated by applying a load to the lever arm which is calibrated as to length. The weight in pounds that the machine will sustain in a 10 minute run without rough scarring or gouging occurring on the lubricating test block is given as the Timken E.P. factor. The instrument was primarily designed for testing fluid lubricants, but has since been adapted for testing grease products. This is done by providing a grease gun which will maintain a constant pressure in lubricant delivery to the test area.

Upon testing the greases of the preceding Examples I, II and III in the Timken machine, it was found that they gave load-carrying capacities of 60 pounds each indicating very good extreme pressure properties.

In order to illustrate the critical nature of the relative concentrations between sublimed blue lead and sulfurized sperm oil in the grease compositions of this invention, Tables I and II are given. Table I sets forth Timken test results for various samples of substantially identical lithium base greases, but difiering mainly in the ratio of sublimed blue lead to sulfurized sperm oil and in the total amounts of these additives.

Table II presents Timken test values for various test samples of calcium base grease compositions. As in the case of Table I, the samples shown in Table II are substantially identical, differing essentially only in the ratio of sublimed blue lead to sulfurized sperm oil and in the total amount of these additives.

In Table I, the grease of sample No. 3 had the following make-up in percent by Weight.

Make'up: percent by weight All of the other samples had an identical make-up, except that where decreasing amounts of the total of sublimed blue lead and sulfurized sperm oil Were employed a correspondingly increased amount of mineral oil base was used.

In Table II, the grease of sample No. 1 had the following make-up in percent by weight.

Make-up: percent by weight- 300 SUS at F. Texas distillate 48.35 Asphaltum oil 20.65 Calcium soap of tallow 19.40 Glycerine 1.90 Water 1.90 Sublimed blue lead 3.90 Sulfurized sperm oil 3.90

As in Table I all of the other samples had an identical make-up, except that where decreasing amounts of the total of sublimed blue lead and sulfurized sperm oil were employed a correspondingly increased amount of mineral oil base was used.

In all examples, the sulfurized sperm oil employed had the following inspection:

Gravity: API 13.0 Viscosity, SUV: Sec. 210 F. 244 Pour: F. +60 Sulfur: percent 12.0

Table 1 Sample Number 1 2 3 4 5 6 7 8 9 10 Percent by Wt.:

(A) Subllmed Blue Lead 5.0 n11 2.6 2.0 2.0 1.3 1.0 0.8 0.6 0.6 (B) Sulfurized Sperm 011 ml 5.0 2.8 4.0 5.0 4.0 4.0 4.1 4.4 5.0

Total (A-l-B) 5.0 5.0 5.4 0.0 7.0 5.3 5.0 4.9 5.0 5.0

Approximate Ratio (A/B) 5/1111 nil/5 1/1 1/2 1/2.5 1/3 1/4 1 5 1/7 1/8 Timken Result a0 14 20 30 as 50 70 90 18 17 Table II sistency with a lithium soap and having incorporated therein from about 2 to 10 percent total weight of a com- Sample Number 1 2 3 4 5 bination of sublimed blue lead and sulfurized sperm oil in a weight ratio to each other of from about 1:3 to 1:5. Percent by we; 5. The grease of claim 4, wherein the mineral lubricat- (A) sublimed 311115116811 ing oil has a viscosity of at least 1000 SUS at 100 F., (B) summed sperm on and the lithium soap comprises a lithium soap of hydro- Total Percent by Wt. (A-l-B)... 7.8 7.8 5.2 6.5 7.8 d Castor 1 Approximate Ratio (A/B) 1 1 1 2 1 3 1 4 1 5 20 6. The grease of claim 4, wherein the sublimed blue Timken Results 45 65 60 lead and sulfurized sperm oil are present in a weight ratio to each other of about 1:4.5.

As is noted in Table I test samples 6, 7, and 8 which 7. A lubricating grease having substantially the followcontain ratios of sublimed blue lead to sulfurized sperm ing approximate composition in percent by weight: oil in the range of 1:3 to 1:5 show outstandingly imr proved extreme pressure properties over other comparapercent welght 500 SUS at 100 F. Texas 011 43.50

We samples. It 15 noted that the total additive concen- I 150 SUS at 210 F. M1d-Cont1nent Bright trat1on of these samplm 1s about the same as, or less Stock 41 10 than the test samples which did not show improved extreme pressure properties. Similar conclusions are api i soap hydrogenated Castor 011 L1th1um soap of tallow 0.90 parent from an mspectlon of Table II. G1 Celine 0 90 It will be understood that conventional additives of the y Sublnned blue lead 1.00 prior art such as rust preventatives, oxidation mhlbltors, sulfurized 5 arm oil 4 50 fillers, antibleeding agents and the like may be added to "1' the compositions of the present invention without depart- 8. A lubricatmg grease comprising a major proport1on ing from the spirit and scope thereof. of a mineral lubricating oil thickened to a grease con- I claim: sistency with a calcium soap and having incorporated 1. A lubricating grease comprising a major proportion therein from about 2 to 10 percent total weight of a of a mineral lubricating oil thickened to a grease conc9m b1nat10n 0f subllmed blue lead and sulfllnzed Sperm sistency and having incorporated therein from about 2 40 011 111 a Weight l'atlo 10 each other of fr m about 1:3 to 10 percent total weight of a combination of sublimed t0 blue lead and sulfurized sperm oil in a weight ratio to T greaseof 61mm Whefeln the mmefal lubrwatea h oth f fr b t1;3 1;5 mg 011 has a viscosity of at least about 1000 SUS at 2. The grease of claim 1, wherein said sublimed blue the Calcium; p comprises the calcium p 05 lead and said sulfurized sperm oil are in a weight ratio and the 'Subhmed blue l and Sulfllfiled Sperm of about 1:4 t 15, 011 are present 1n a weight ratio to each other of about 3. The grease of claim 1, wherein the mineral lubricating oil has a viscosity of at least about 1000 SUS at 100 F. and is thickened to a grease consistency with a References cued m the file of fins Patent UNITED STATES PATENTS soap.

4. A lubricating grease comprising a major proportion of a mineral lubricating oil thickened to a grease con- 

